I love a mystery, and nature has many.
Each morning shortly after dawn, a flock or two of Canada geese take off from a nearby farm pond and head out for one of the surrounding ponds and a day of grazing and lazing. It’s hard to miss them as they fly over the neighborhood discussing which salad bar offers the best deal of the day.
On my commute to work, I pass a different farm pond. Yesterday, the pond held two pairs of ring-necked ducks and several green-winged teal. Today the green-winged teal are gone, but a pair of hooded mergansers has replaced them. The ring-necked ducks are still there.
This happens all the time. Ducks play musical chairs — or rather, musical ponds. They are in a pond for a day or a week or so and then disappear only to reappear a few weeks later.
A while back, I realized that with all the movement between ponds, I should be seeing a lot more ducks flying about the valley. It’s not like I never see ducks on the move, just not that many. Geese are up and about all the time, but ducks seem to have different flight plans. Other waterbirds also seem to magically appear and disappear. I can count on one hand the number of coots I have seen flying about the valley unless flushed, and coots are even long-distance migrants.
Since then, I have been paying closer attention.
This time of year I often find myself heading home as the last light is fading from the sky. I have come to realize it’s at this time I see numerous ducks in flight. There are pairs and small flocks in a hurry from one spot to another. They are just silhouettes against a fading brick-red sky, and I am unable to identify most. But they seem as busy as the rest of the commuters in the valley.
Is it safety that prompts the other ducks and waterbirds to conduct most of their travels in the dark? What threats are greater in the daylight? I can think of few. At one time peregrine falcons were known as duck hawks. Yes, they take ducks, but there just aren’t that many falcons about. Then there are northern harriers and the occasional ambitious red-tailed hawk.
Duck hunters hunt during the day, but it’s hard to believe the hunters at Denman and a few other areas are enough to affect the behavior of waterbirds across the valley.
There are many more duck predators active at night, including coyotes, bobcats, raccoons, opossums, mink and great-horned owls. It seems hazardous to drop in on a pond not knowing what predators may be about.
The other possibility is that they are traveling to feeding areas. Different species have different behaviors. Some feed largely during the day, such as American wigeon and ring-necked ducks. Others, like northern pintail and gadwall, feed more at night and tend to loaf all day. These species tend to travel to feeding areas after sunset. Still, I’m not sure why they wait until darkness.
I have no answers to this minor mystery, but somehow I find it comforting that there is so much we don’t know. If anyone has any knowledge or insights, I’m eager to hear from you.
Stewart Janes is a biology professor at Southern Oregon University. He can be reached at firstname.lastname@example.org.